Adjusting Brake Response
: The spring in the brakes tend to push the pads away from the rim. Tightening the cable pulls the pads closer to the rim while loosening the cable allows the pad to move away from the rim. If the brake are to sensitive (pads to close to rim) or not sensitive enough (pads to far away from the rim), hold the brake pads against the rim with one hand and with the other turn the brake adjustment barrel
: counter clockwise
to move the barrel screw up, tightening the cable, and moving the pads closer to the rim
or clockwise to move the barrel screw down, loosen the cable and move the pads away from the rim (figure 1).
One of the new Shimano barrel adjuster (black four sided adjuster - figure 2) works in exactly the opposite direction: Clockwise to move the barrel up, tightening the cable and move the pads closer to the rim and counter clockwise to move the pads away from the rim. And still another has a black barrel similar to that in the video above and work in a similar manner (figure 3). With this later barrel, be sure to hold the lower nut while turning the barrel.
What if the bake adjusting barrel is at it's limit, all the way in or all the way out?
As shown in the video, the brake pads are held against the rim with one hand and the cable bolt is loosened. Next release the brakes to give about 1 or more mm of clearance, tug on the brake cable to make sure it's taut, and the tighten the cable bolt. If this brake adjustment is to difficult, there are some tools to assist as explained below.
: Bake adjustment also involes the centering of the brakes so that the brake pads are an equal distance from each side of the rim by using a 3 mm Allen wrench on the "centering adjustment bolt" (figure 4). This bolt is on the top of the brake calipers (the arms that hold the brake pads), on the opposite side of the brake cable. Turn the bolt clockwise to move the calipers right and counter-clockwise to move the calipers left. If this fails to center the brakes, adjustment should be done by loosening the bolt on the brake bridge as shown in the video.
Tool to assist in adjusting brake sensitivity: I use an Irwin Quick-Grip Mini Bar Clamp (figure 4) for bake adjustment. Release the bolt that holds the brake cable with the proper Allen wrench. Turn the brake adjusting barrel (figure 1) such that half the threads show above and below. Place the clamp ends through the spokes and clamp the brake pads leaving a millimeter or 2. Give a tug on the brake cable so it's taut and then tighten the brake cable bolt. Remove the Quick-Grip clamp carefully so as not to damage your wheel or spokes. Use the adjusting barrel to fine tune the space between the bake pads and wheel rim.
Get rid of the "squeek" and prevent sudden stops: Adjust the front of the pad to be 1/2 mm closer to the rim than the back of the pad ("toeing" the brake pads). The purpose of building this slant into the brakes is to make braking more gradual. The more you squeeze the brakes, the more contact the brake pad will make with the rim. If you don't build this angle into the brake pad, the entire pad will fall onto the rim at once, as soon as you brake. Such sudden braking can lead to an accident, especially in corners. Many models of Shimano caliper brakes allow you to rotate one end of the pad closer to the rim than the other.
One can also use a Tacx Brake Shoe Toeing Tool availabe from Cambria Bicycle Outfitter.
Loosen the brake cable bolt and turn the brake adjustment barrel such that half the thread show above and below. When using, make sure that the arrow in front of "Tacx" on the plastic clamp is pointing forward at allow correct "toeing." Apply the Tacx tool on the rim with the top of the tool just settled on top ot the rim. Use your hands or a mini-clap to press the pads against the Tacx and proceed as above. You may need to loosen the brake pad mounting bolt (see Maintenance Tips - Bike Anatomy) to align the pads against the top rim of the Tacx which will give the pads the correct orientation against the rim when the Tacx is removed. (don't forget to then re-tighten). To remove the Tacx tool, just open the brake quick release (as you do when you remover the wheel). Turn the wheel to move the Tacx from under the brake pads. Finally, remove the Tacx and reclamp the brake quick release. As you can see in figure 6, the Tacx tool is tappered to allow one end of the brake pad to be closer to the rim then the other end.
Additional Video on Brake Adjustment